I've built 5 bikes with Chinese motors and had no problems until my last 3 kits. Installed in a 70's cruiser frame and vibrated very badly at speeds above 15 mph or so. Next motor did the same so I made a head brace to triangulate the mounting. It helped but is still not right. Bought a more expensive kit and it's better even without the extra brace, but not nearly good enough to give to my friend I built it for. I'm going to try a head brace on it also but it has smaller head bolts and will have to make a new one. My question is does it make a difference what frame you put these motors in? Would more substantial frame clamps help? The thin sheet metal clamps that come with the kit seem to stretch and distort easily and may not hold tight enough. I have a Panama Jack bike for my next project and will know in a couple of days if it shakes too much.